Recognizes a protein of 52kDa-58kDa, identified as CD46 (also known as membrane cofactor protein, MCP). Its epitope is located on the four immunogenic short consensus repeat (SCR) domains at N-terminus of the protein. CD46 exists as many isoforms in a variety of tissues. It is strongly expressed on salivary gland ducts and kidney ducts, moderately on lymphocytes and endothelium, and weakly on interstitial tissues and muscle cells, but not on erythrocytes. CD46 functions as a C3b/C4b-binding glycoprotein that inhibits complement activation on host cells. It also serves as a measles virus receptor, an adherence factor for group A Streptococcus pyogenes, and a cellular pilus receptor for pathogenic Neisseria.